Control apparatus for internalcombustion engines



May 25, 1948. v L 1 2,442,049

CONTROL APPARATUS FOR INTERNAL-COMBUSTION ENGINES Filed Sept. 19. 19 6- 3 Sheets-Sheet 1 NOREASE PUMP oeuvem TOI/ GEAR SHIFT (Has) mvau'roR LBJQHTU ZBBI AGENT &

L. LEE, 2D 2,442,049 CONTROL APPARATUS' FOR INTERNAL-COMBUSTION ENGINES May 25, 1948.

3 Sheets-Sheet 2 1 Filed Sept. 19, 1946 IN V 2N TOR. E 727 1-75 gig/9H N Aesni May 25, 1948 E 25 2,442,049

CONTROL APPARATUS FOR INTERNAL-COMBUSTION ENGINES 3 Sheets-Sheet 3 Filed Sept, 19, 1946 H T0 INJEOTOR\ o 212 PUMP moans: DELIVERY PUMP 270 CONTROL -J DELIVERY Fig.5

0000coomuoonncoonooo- 202 INVENTOR, ;EIQTUN ZIL'L'H I AGENT flow so as to Patented May 25, 1948.

CONTROL APPARATU COMBUSTIO Leighton Lee, H, Rocky mesnc assignments,

of New Jersey s FOR INTERNAL- N ENGINES Hill, Conn.,' assignor, by

to Niles-Bement-Pond Company,'West Hartford, Conn., a corporation Application September 19, 1946, Serial No. 697,873

11 Claims.

This invention relates to control apparatus for internal combustion engines, and particularly to apparatus for regulating the flow of fuel and/or air to the engine so as to maintain a selected fuelair ratio. Although the invention is illustrated as applied to a conventional type of reciprocating engine, it should be readily apparent that its principles are equally applicable to other types, such as the turbine and Jet types.

In most modern internal combustion engines,

- particularly those used on aircraft, the fuel-air .ratio is controlled by measuring the air flow,

measuring the fuel flow, and using a comparison of these two measurements to regulate the fuel maintain a selected fuel-air ratio.

The conventional way of measuring the air flow is through the use of a Venturi meter to produce an air pressure differential which measures the 1 volume of air flowing to the engine per unit time. Such meters are subject to at least two disadvantages. In the first place, if the Venturi meter is made large enough to handle the large volume of air required at maximum power output, then the air pressure differential which it provides at low air flows, as under engine idling conditions, is so small that it is not practically usable. the second place, the density of the air varies considerably, especially in aircraft which must operate through a wide range of air temperature and pressure conditions.-- Therefore additional mechanism must be provided to compensate the air flow measuring device for variations in air density.-

The measurement and control of the fuel flow in the conventional eral problems. The fuel flow is usually measured by taking the pressure drop across a fixed metering orifice as a measure of the fuel flow. This is satisfactory unless the fuel vaporizes at the orifice, or if there is vapor present in the fuel flowing to the orifice. The presence of vapor destroys the fixed relationship between the fuel pressure differential and the rate of fuel flow, so that the fuel pressure differential is then not an accurate measure of the fuel flow. Since the fuels commonly used on aircraft have a strong tendency to vaporize, this difliculty requires careful consideration in a design of a fuel system. The fuel flow is commonly controlled by means of one or more valves. These valves must operate over a relatively wide range of fuel flows and must control the fuel flow accurately at any point within that range. Because of these requirements, the valves are quite sensitive structures. and therefore are adversely affected by vibration.

type systems also present sevmechanism which An object of the present invention is to provide an improved apparatus for controlling the fuel air ratio in an internal combustion engine.

Another object is to provide improved means for measuring the rate of flow of air through a compressor.

Another object of this invention is to provide an improved control system for an internal combustion engine where the temperature rise of the air flowing through a compressor, or supercharger, associated with the engine and the torque required to drive the compressor are together f utilized to provide a measure of the rate of flow of air.

A further object is to provide improved control apparatus for an internal combustion engine having an air compressor wherein the compressor torque, the temperature rise across the compressor, and the rate of fiow of fuel to the engine per engine revolution are combined to control a servomotor for regulating the fuel-air ratio.

Another object is to provide an improved system of the type described, wherein an injector pump is used to supply fuel to the engine, and the delivery setting of the injector pump is utilized as a measure of the rate of flow of fuel to the engine per engine revolution.

\ Other objects and advantages of the present invention will become apparent from a consideration of theappended specification, claims and drawings, in which: 1 v

Figure 1 shows, somewhat diagrammatically, a control system for an internal combustion engine embodying the principles of my invention,

Figure 2 illustrates in detail a torque responsive variable resistance shown diagrammatically in Figure 1,

Figure 3 shows in greater detail an electrical gear-shifting mechanism shown diagrammati cally in Figure 1,

Figure 4 illustrates a manually operable control is associated with the system of Figure 1, and Y -Figure 5 illustrates tric'al circuit used in the system of Figure 1.

Referring to Figure 1, there is shown a sectional view through the cowling it) around an aircraft engine generally indicated at [2. The engine I! drives a propeller whose hub portion is shown at I4.

Mounted on the back of the engine is a supercharger it having an impeller i8 fixed on a shaft 20. The shaft 20 is hollow, and anothershaft 24 rotates inside the hollow shaft 20. The two shafts 20 and 24 are connected by suitable gearing shown a wiring diagram of an elec- Y the engine.

impeller I8.

plementary throttle blades schematically at 28 ure 2 of the drawing. The shaft 24 extends beyond the end of shaft 28 and drives a fuel injection pump mechanis The injector pump. mechanism 28 is provided with a fuel inlet 88 and with a plurality of fuel outlets 82 leading to the individual cylinders of The 'outlets 82 may alternatively deliver to the intake manifold Just outside the engine cylinders, or they may deliver to a common discharge nozzle located in the supercharger inlet.

Combustion'air flowing to the engine passes thru an air scoop 84- projecting above the cowling I8 and thence through a throttle body 88, and a supercharger inlet conduit 88 to The air'is discharged peripherally from the impeller I8 into the intake manifold 48, from whence it flows into the engine cylinders.

The flow of air is controlled by a pair of com- 42, which are fixed on shafts 44. Each shaft 44 is provided with an arm 48, and the ends of the arms 48 are connected by a link 48 so that the throttle blades 42 move concurrently. One of the shafts 44 is provided with .a gear sector 88 which engages a worm 52 driven by a motor 54, so that the throttle blades are positioned by operation of motor 84.

One of the shafts 44 is provided with a switchoperating finger 88. In the position shown, the switch finger 88 has engaged a contact finger 88, moving it into engagement with a stationary contact finger 88. The contact fingers 88 and 88 form part of an electrical circuit for the operating mechanism of a gear shift 22, to be later described.

The switch-operating finger 88 also co-operates with a movable switch erates with two stationary switch fingers 84 and 88, and together with them forms a double throw "switch mechanism generally indicated by the number 88. The switch mechanism 88 forms part of a control circuit for a gate motor I12 shown in Figure 4. v 1

A pair of electrical resistance elements 18 and I2 are mounted in the inlet conduit 88 so as to be the entrance of and in greater detail in'Fig-' a finger 82, which co-opexposed to the temperature of the air flowing through that conduit. These may consist of an electrical resistance element mounted in a metal shell, in a manner well known in the art. The resistance element 18 is connected by a pair of conductors 14 and 18 to a power supply and amplifier unit generally indicated at I8. Resistance 12 is connected to the unit I8 by a pair of conductors Y88 and 82.

Another pair of temperature responsive resistresistance. bulbs ance elements 84 and 88 are mounted so as to be exposed to the temperature of the air on the discharge side of the supercharger I8. Resistance element 84 is connected to the unit 18 by a pair of conductors 88 and 88. Resistance 88 is similarly connected to the unit 18 by a pair of conductors 82 and 84.

The gearing 28, which is shown in greater, detail in Figure 2. includes a variable resistance 88, which is varied in accordance with the torque required to drive the supercharger impeller I8.

The resistance 88 is connected to the unit 18 through conductors 88 and I88.

The injector pump mechanism 28 includes able apparatus for varying its delivery per revolution. This injector pump and its delivery control mechanism may be constructed in accordance with that shown in the co-pending applicasuitshift mechanism shown schematically at 22 in tween conductors 88 with the pilot's control mechanism shown in detail in Figure The opposite end of arm I82 is provided with a contact finger I88 which engages a resistance I88. The'resistance of element I88 is thereby varied in accordance with the delivery per revolution of the pump mechanism, and hence the resistanceof element I88 may be said to be a measure of that delivery. One terminal of resistance I88 and the contact finger I88 are connected by conductors H8 and I I2, respectively, to the unit I8.

The motor 84 is connected to the unit 18 by six conductors H4, H8, H8, H8, I28 and I2I.

The gearing mechanism 28, as'shown in detail in Figure 2, includes a sun gear I22 fixed on the shaft 24, three planet gears I24 fixed on a spider I28, and a ring gear I28 connected by means not shown to the hollow shaft 28 which drives the supercharger impeller i8.

The spider I28 is provided with an upwardly extending arm I38, biased to the left by a spring I82.

The end of arm I88 carries an insulated, slidin8 contact finger I84 which rides on the resistance element 88. Contact I84 is connected by a conductor I88 to the left terminal of resistance 88. The shaft 24 and gear I22 rotate clockwise, as indicated by the arrow in the drawing. This drives the planet gears I24 counterclockwise about their respective pivots, ring' gear I28 counterclockwise. A clockwise torque is thereby applied to the spider I28, and this torque is proportional to the torque transmitted to the ring gear I28 to drive the supercharger impeller I8. The torque applied to spider I28 is resisted by spring I82, which is thereby deflected, allowing the slider I84 to move along the resistance 88. A stop I88limit's the leftward movement of arm to zero torque. The left end of resistance 88, as it appears in Figure 2, is connected to a. conductor 98, and its right end is connected to a conductor I88. Slider I84 is connected to a conductor 248. As the slider I84 moves to the right along resistance 88, the resistance between conductors 88 and 248 isincreased. When the arm I88 is in its zero torque position, the resistance between conductors 88 and 248 is zero. As'the slider I84 moves to the right, the resistance be- I and 248 is gradually increased in proportion to the torque required to drive the supercharger or compressor.

Figure 3 illustrates in greater detail the gear Figure 1. Referring to Figure 3, it will be seen that the shaft 24 passes completely through the gear shift casing 22. The left portion of shaft 28 terminates in a gear I48, which mate with a gear I42 carried by a shaft I44. The shaft I44 extends through a gear carries at its opposite end another gear I48, which engages the gear I88 atJzhe left end of the right-hand section of shaft 28.

The gear shift mechanism I48 may-be of any conventional type. It includes a controrarm I82 movable from the low-speedposition indicated in the drawing to a high-speed position which is displaced clockwise from the position shown. The end of arm I82 is pivotally attached to an armature I84 which co-operates with a pair of electromagnets I88 and I88. when elecand thereby drives the I88 in a position corresponding shift mechanism I48 and tromagnet I88 is energized. by an electrical circuit to be described later, the armature I84 is drawn to the left, thereby operating the arm I82 to its high-speed position. When electromagnet I88 is energized, the armature I84 is drawn to the right, thereby operating arm I82 to its low-speed position. The upper end of arm I82 co-operates with a pair 01 switches I80 and I82. 4

Figure 4 illustrates the pilot's control mechanism by which the link 104 which actuates the pump delivery control oi I02 is operated. There is shown in Figure 4 anextension or the link I04 oi. Figure 1. link located quite remote from link I04, but connected thereto through suitable mechanism so that the two move concurrently. The upper end of link I04 of Figure 4 is connected by alink I82 to a lever I84 pivotally mounted on a-shait I88. There is also mounted on the shaft I88, for free rotation thereon, a sector gear I88, which engages a worm I10 driven by a motor "2.. The gear I88 is provided with a long leftward extension I14 which carries a stop I18 projecting forwardly into the path or lever I84. The tip of projection I14 serves as an operator i'or a switch mechanism I18. The switch mechanism I18 includes a stationary contact finger I80, and

' a movable contact finger I82.

There is shown in Figure a wiring diagram illustrating in detail the connections between This may alternatively be another the various circuit elements which are shown in Figure 1 as being connected to the amplifier and power supply unit 18. Referring to Figure 5, it may be seen that the system is supplied with electrical energy through a transformer 200, having a primary winding 202 and secondary windings 204, 208, 208,.2I0 and 2I2. The winding 208 supplies electrical energy to a series circuit including resistance element 84, resistance element 10, and afixed resistance 2I4. The

potential drop across resistance 84 in this circuit may be expressed by the following equation:

srlm'i m where E represents the terminal voltage of the secondary winding 208, 1 represents current. and the various R characters represent the resistance of the element indicated by their associated subscripts. The secondary winding 208 supplies electrical energy to a series circuit including a fixed resistance '2I8 and temperature responsive resistance elements 12 and 86. The potential drop across resistance 12 in this circuit may be expressed by the following equation:

R12 ao+ R214 The secondary windings 208 and 208 are designed to have the same terminal voltage, indicated by the letter E.

The potential drops across the resistances 14 and 12 are connected in series opposition in an external circuit by means of conductors 2I8, 220 and 222. Therefore the potential drop between the conductors 2I8 and 220 may be expressed by the following equation:

If the resistance of the elements 2I4 and U6 is made large as compared to the resistance of elements 10, 12, 14 and 88, then it may be considered that the denominator of the expression in the right-hand side of Equation 3 is a constant. Alsoit ma be considered that the current flows through the two series circuits considered above are likewise constants. Then it follows that the potential drop between conductors 2I8 and 220 is determined by (Ru-R12). But (Ran is a measure of the supercharger discharge air temperature. and (R12) is a measure of the supercharger inlet air temperature, so that the potential drop between conductors 2I8 and 220 is a measure of the temperature rise across the supercharger I8. Hencethatpotential drop may be expressed by (Tn-T1), where (T2) is the supercharger discharge temperature and (T1) the supercharger inlet temperature.

The secondary winding 2I0 impresses a potential across the terminals of the resistance I08. For a given value 01' variable resistance 2 and a given position of switch 2I3, this potential is fixed. The slider I08 is moved along resistance I08 in a manner so that the potential between slider I08 and the right end of resistance I08- varies inversely with the setting of the pump delivery control arm 0. This potential is impressed across the resistance 88. The slider I34 which co-operates with resistance 88 is arranged to change its position so that the resistance between slider I34 and the right end of resistance 88, asit appears in Figure 5, varies as the torque required to drive the supercharger L. Since the total potential across the whole resistance 88 is inversely proportional to the setting of the pump delivery controller, then the potential be- 4 the inward terminals otan amplifier including a pair of gas-filled discharge tubes 224 and 228. The tube 224 has an anode 228. a control electrode 230, and a cathode 232. The discharge tube 228 has an anode 234, a control electrode 238, and a cathode 238.

The discharge devices 224 and 228 have a common input circuit which may be traced from the control electrodes 230 and 238 through conductor 240, slider I34, resistance 88, conductor 220, resistance' 12, conductor 222, resistance 84, and conductors 218, 242 and 244 to the cathodes 232 and 238. v I

The output circuit of. the discharge tube 224 may be traced from anode 228, through conductor I2l, field winding 248 of motor 84, a condenser 24.8 in parallel with the winding 248, conductor II8, transformer secondary winding 2l2, conductor II8, armature winding 280 of motor 84, and conductors 2i8 and 242 to cathode 232.

The output circuit of discharge tube 228 may similarly be traced from anode 234 through conductor I20, field winding 282 and its parallel condenser 284, conductor II4, secondary winding 204, conductor II8, armature winding 280, and conductors 2I8 and 244 to cathode 288.

It should be noted that the secondary windings 2M and H2 are connected in phaseopposition in their respective circuits. That is, the left terminalot winding 204, as it appears in the drawing, is connected to anode 234, while the right terminal oi winding 2l2 is connected toanode 228. Since the windings 204 and M2 are secondaries on the'same transformer, it should be apparent that the discharge tubes 224 and .228 may become conductive only on opposite halt cycles. Since their common input circuit includes two potentials connected in phase opposition, one tube will become conductive when onepotential predominates over the other and the other tube will become conductive when the second potential predominates. When the two are equal and balanced, neither tube will become conductive, or both will become conductive equally. If desired, suitable biasing voltage means may be inserted in the common input circuit to keep the both tubes inoperative when the input potentials are balanced. The field windings 248 and 252 of motor 54 are so related to the armature winding 25!! that the motor runs in one direction when winding 248 is energized and in the opposite direction when winding 252 is energized.

If the motor 54 drives the throttles in an opening direction, this increases the air flow, thereby increasing the torque required todrive the supercharger and decreasing the temperature rise oi the air compressed by the supercharger. On the other hand, if the throttles are driven in a closing direction, then the quantity of air is decreased, decreasing the torque required to drive the supercharger, but increasing the temperature rise of the air through the supercharger.

From the foregoing, it may be stated that the motor 54 is controlled applied to maintain the following equation in balance:

,L T -T A which is readily recognized as a transformation of the expression set forth in (4) above.

Equation 5 may-alternatively be written:

It will now be proven mathematically, that ii the system operates to' maintain Equation 5 in balance, then it operates to maintain a constant fuel-air ratio.

. The power required to drive a centrifugal compressor may be expressed as follows (The Engineer's Manual, by Ralph G, Hudson, second edition (1939), page 178, Equation 721):

where Converting all pressures to units of pounds per square root (indicated by P2, P1)- and power to horsepower units (indicated by HP). and subvalue for stituting the numerical 11. Equation 6 becomes:

From Boyle's law and Gay-Lussac's law, we

have the well-known relation:

iVi

-TT A R where II P= Here A represents the air flow in pounds per minute. The change of state, produced by an air compressor of the type under consideration may be considered to be a polytropic one. For such a change,

'n-i 'll a Tl v 10 or as will P 'It I T.=T,( f) 11 and 1L T,- T, T,[(%) 1] 12 Substituting 12 in i), we get HP: KA (7' -'I,) (13 v where K is a constant.

From fundamental relationships,

HP=L RPM, K, 14

where L is torque. V 7

RPM. is revolutions per minute of the supercharger and K1 is a constant depending on the units used.

Equating 13 and 14, we get K A(T T )=LXRPM, (15) L RPM, 60 a'";$ T (16) where K: and K: are constants. v

Equation 16 gives a direct, easily measurable v indication of mass air flow per unit time, which 65 requires no altitude or density correction.

The fuel flow per unit time may be expressed as constant depending on the units used If a constant fuel-air ratio is maintained, then, dividing 17 by 16 but RPMp/RPM. is aconstant, since both pump and supercharger are engine driven, so Equation 7 18 reduces to L To 1 K76 10 across resistance I88 by moving the throttles slightly toward closed position, whereupon the contact finger 82 is separated from contact finger 88 to interrupt the motor circuit just traced.

After the stop I18 has moved a predetermined distance in a fuel flow decreasing direction, then the tip of projection I14 moves upward into engagement with switch finger I82, moving the latter to the left and into engagement with contact I88. This completes an energizing circuit for the high speedelectromagnet I88 01' the gear-shifting mechanism I82. This circuit may be traced from the left terminal of battery 214 (Figure.v 1) through aconductor 21'8, switch finger I88 (Fig-.- ure 4), switch finger I82, conductor 218, switch I82 (Figure 3) conductor .288, electromagnet I88, conductor 282, and giound connections 284 and .288 to the right terminal of battery 214. Energization of electromagnet I88 causes operation of v at any given throttle case, the control system would maintain a constant fuel-air ratio.

When the throttle reaches its full open position, and the automatic system calls for a further increase in air flow to maintain the selected fuelair ratio, such increase cannot be obtained by operation of the throttle. Under such conditions, it is necessary that the fuel flow be decreased to produce the required fuel-air ratio, rather than increasing the air flow. This is accomplished by the switch mechanism 88, which controls the motor I12 (Figure 4), which positions the manual lever stop I 18. v

The switch finger 82 is self-biased into engagement with stationary contact finger 84. At such times, a circuit is completed for energizing motor I12, which may be traced from the left terminal of battery 214 (Figure 4) through a conductor 288, switch finger 82, switch finger 84, conductor 284, motor I12, conductor 282, and ground connections 218 and 288 to the'right terminal ofbattery 214. This circuit energizes motor I12 for operation in a direction to drive stop I18 away from lever I 84, so that the stop does not limit the movement of the lever. This circuit is interrupted when the stop reaches the end of its travel by a limit switch built inside the motor I12 and not shown in the drawing. I When the throttle reaches its full open position, the finger 88 engages switch finger 62, moving it out, of contact with stationary contact 84,.

and moving it into engagement with stationary contact 88. This completes another circuit for energizing motor I12, which may be traced from the left terminal of battery 214 through conductor 288, switch fingers 82 and 88, conductor 212, motor I12, conductor 282, 'and ground connections 218 and 288 to the right terminal of battery 214. This circuit energizes motor I12 for operation in a direction to-drive stop I18 toward the lever I 84 so as to limit the movement of the latter in a fuel increasing direction.- In fact, the energization of this circuit continues until stop I18 engages lever I84 and pushes it upward in a fuel flow decreasing direction. This movement continues until the automatic control circuit responds to the continued operation of slider I88 shift, I have provided the electrical potential to its high I12 to retract the stop If, with the supercharger gear-ratio control in be a constant in making the gear-shifting mechanism to its high speed position, thereby driving the supercharger at a faster rate, and increasing the air flow available position. As the gearshifting mechanism moves to its high speed position, the circuit justtraced is broken at switch I82. The resulting and sudden increase in the air fiow restores control to the balanced control circuit, which closes the throttles partially, thereby restoring switch mechanism 88 to its original position and thereby causing operation of motor I18 away from lever I84.

its high speed position, the aircraft should return to a lower altitude where sufllcient air could be obtained without the high speed drive, the balanced control system will gradually close the throttles until the finger 88 engages switch 88 and moves it into engagement with switch finger 88. This completes an energizing circuit for the low speed electromagnet I 58 of the gear-ratio control mechanism I28. This circuit may be traced from the left terminal of battery 214, through conductor 288, switch-fingers 88 and 88, conductor 288, switch I88, conductor 282, electromagnet I88,

conductor 284, andground connections 284 and .288 to the right terminal of battery 214. The

supercharger is thereby shifted to low speed operation, and the resulting sudden decrease in air flow causes operation of the throttle servo-motor to restore the selected constant fuel-air ratio.

When the gear ratio control is shifted from its low speed to its high speed position, or vice versa. the ratio RPMp/RPMs, which was considered to the transformation from Equation 18 to Equation 19, above, is changed. The ratio is decreased on moving the supercharger from low speed to high speed position, and increased on the opposite move. If it requires a. given torque to move a given quantity of air through the supercharger at low speed, then it requires a greater torque to move the .same amount of air through the supercharger at high speed. on resistance 98 may'serve as a true measure of torque in either position of the supercharger gear mechanism for reducing applied to the terminals of resistance 98 Whenever the gear shift is moved speed position. This mechanism includes a double-throw switch 2I3. This switch 2I3 is operated concurrently with the gear shift, as indicated in Figure 3. The switch 2 I3 includes a finger 388, self-biased into engagement with a contact 382. A block 388 is mounted on the finger 388, and lies in the path oi movement of In order that the position of slider I84 I slightly too great armature till. When the gear shift is moved to its high speed position, block 308 and moves finger 300 out of engagement with contact- 302 and into engagement with a contact 304. Finger 300 is connected through conductors 220 and 98 to the right end of resistance 98. Contact 302 is connected through a conductor 308 to the right end .of transformer secondary winding 2H3. Contact 80 is connected through a conductor m to a secondary winding M at a point spaced from its right end. Therefore the eflect of moving finger 300 from contact 382 to contact sons to reduce the potential across resistance 88. Thus when the gear shift is moved from low to high. the potentialacross resistance 98 is reduced. While the increased torque due to the increased speed of the supercharger may cause a, deflection "of slider I along resistance 9 8. the reduced potential across resistance 96 compensates for the increased deflection of slider I34 so that the potential between slider I34 and conductor 220 continues to be a true measure of torque.

A variable resistance 2i i is connected between the left end of resistance l08-and the left end of secondary winding 2H3. This resistance is manually variable, and ismounted so that it may be manipulated by the pilot or other member of the aircraft crew. By varying resistance 2, the

potential applied across resistance I08 may be varied to change the fuel-air ratio. In this way. the pilot may select any desired fuel-air ratio within the range of operation of resistance 2| I:

In the control system described herein, acceleration of the engine tends to produce a richer fuel-air ratio than normal. This is to be. contreated to the tendency of a conventional fuel supply system to run lean during acceleration. Conventional systems are commonly supplied with acceleration pumps and other devices to make them run richer during acceleration. Such additional equipment is unnecessary in the present system. When it is desired to accelerate the engine, the injector pump control is manually moved, which in itself has a tendency to produce a rich mixture because of the unavoidable la before the system responds to open the throttles and increase the air supply. Furthermore, the resulting increase in engine speed will accelerate the supercharger, and an additional torque will be used in accelerating the supercharger. This additional torque will be measured by the fuel control systemand will indicate to the system an air flow somewhat greater than the actual air flow. As long as this transient accelerating torque appears in the system, it will cause the fuel-air ratio to be richer than normal, since the air flow measurement-by the system will be as compared with actual air flow, and the system will tend to balance out with an air flow less than tain the preselected fuel-air ratio. As soon a the transient accelerating torque disappears, the fuel-air ratio is restored to its-normal value.

In the system described, the sensitivity of measurement of air flow and fuel flow is the same under low flow conditions as at maximum flow conditions. The conventional fuel supply sys-- tems require special controls for idling conditions, which are not needed in the present systern. 1

Another advantageofthe present system is that no venturi is require in the air stream. Inconventional systems, the maximum possible engine ower output is limited by the area of t e tap 3l2 located on that required to mainthe armature I enga es ture is also simplified as compared with conventorque required .ployed are for use as uring means for. controlling air venturi throat, since that in the air supply conduit. 'Nosuch limitation exists'when the present system is used. The air supply system can therefore be designed with greater freedom and better air distribution to the cylinders of a multiple cylinder engine can be secured.

In the system disclosed, the fuel conduit structhe absence .of fuel in the fuel conduit. which I have emtional systems, because of flow measuring lets or orifices The terms and expressions not of limitation, and I have no intentionin the use of such terms and expressions, of excluding any equivalent of the features shown and described or portions thereof, but recognize that various modifications are possible within the scope of the invented claims.

I claim as my invention: 1. Control apparatus for an internal combustion engine having an air compressor for supplying combustion air thereto, comprising means for measuring the torque required to drive said compressor, means for measuring the increase in temperature of the air in passing through said compressor, and means including both said measthe flow of air to said sociated with both said measuring means for utilizing the ratio of torque to temperature rise as a measure of fluid flow.

3. Control apparatus for an internal combustion engine having an air compressor for supplying combustion air thereto, comprising manually operable means for controlling the rate of flow of fuel to said engine, means for measuring the to drive said compressor, means for measuring the increase in temperature of the air passing through said compressor, and means responsive to said manually operablev means and to both said measuring means for controlling the flow of air to said engine.

4. Control apparatus for an internal combustion engine having an air compressor for supplying combustion air thereto, comprising injector pump mechanism driven by said engine for deliverlng fuel thereto, manually operable, means,

for varying the quantity of fuel delivered by said engine.

5. Control apparatus for an internal combus-' tion engine having an air compressor for supplying combustion air thereto, comprising: manually operable means for controlling the quantity of fuel supplied to said engine per revolution (C), means for measuring the torque (L) required to drive said compressor, means for measuring the increase in temperature (Ta-T1) of the air passing through said compressor, and means responsive to said manually operable means and to both said measuring means for controlling the flow is the smallest area terms of description and, I

air to said engine so than those of said first and sistances in 13 of air to said engine so as to maintain the following relationship:

1'24. where K is a constant.

6. Control apparatus for an internal combustion engine having an air compressor for supplying combustion air thereto, comprising injector pump mechanism driven by said engine for delivering fuel thereto, manually operable means for varying the quantity of fuel delivered by said pumpmeansl per revolution of said engine, means for measuring the torque (L) required to drive said compressor, means for measuring the increase in temperature Ta-T1) or the air passing through said compressor, and means responsive to said manually operable means and to both said measurin mcans for controlling the fiow of as to maintain the following relationship:

up [(11 Wt-7', where K is a constant.

7. An electrical network for measuring the difference between first and second temperatures, comprising a first pair of substantially similar electrical resistance elements having an appreciable temperature coefilcient of resistance and exposed to said first temperature, a second pair of substantially similar electrical resistance elements having an appreciable temperature coefilcient of resistance and exposed to said second temperature, a pair of fixed electrical resistance elements having resistance values substantially greater second pairs, a pair of sources or electrical energy, a pair of electrical circuits, each of said circuits'including, in series, one of said sources and one 01' each of said pairs of resistance elements, and a third electrical circuit including the one or said first pair of resistances connected in One of said pair of circuits and the one of said second pair of resistances connected in the other of said pair of circuits, the resaid third circuit being connected in series so that the potential drops across them are in opposition and the potential across the two re-. sistances in series in said third circuit is a measure of the difference between said first and second temperatures.

8. Electrical apparatus for measuring the ratio of two variables, comprising a source of electrical energy, a first impedance element connected across said source, a slidable contact movable along said element, means responsive to one 01' said two variables for moving said contact along said impedance element so that the impedance between said contact and one end'of said element varies inversely as one of said variables, a second .impedance element connected between said one end of said first element and said contact, a second contact slidable along said second element, and means responsive to the other of said two variables for moving said second contact along said second element so that the impedance between said second contact and said one end of said first element varies directly as the other of said variables. and the potential between said second contact and said one end of said first element varies as the ratio of said two variables.

9. Control apparatus for an internal combustion engine having an air compressor for supplying combustion air thereto, comprising manually operable means for controlling fuel supplied to said engine per revolution, a first of electrical energy.

- and means responsive 65- contact and one end of said elements varies inversely as the quantity of fuel suppliedper engine revolution, means for measuring the torque required to drive said compressor, a second electrical impedance element connected between said one end of said first element and said contact, a second contact slidable along said second element, means associated with said torque measuring means for moving said second contact along said second element so that the impedance between said second contact and said oneend oi said first element varies directly asv said torque and the electrical potential between said second contact and said one end of said first element varies as the ratio of said torque to the quantity or fuel supplied to the engine per revolution, a firstpalr of substantially similar electrical resistance elements having an appreciable temperature coeflicient of resistance'and exposed to the temperature of the air at the inlet of said compressor, a second pair of substantially similar electrical resistance elements having an appreciable temperature coefllcient of resistance and exposed to the temperature of the air at the outlet of said compressor, a pair of fixed electrical resistance elements having resistance values substantially greater than those of said first and second pairs, a pair of sources a pair of electrical circuits,

each of said circuits including, in series, one of said pair of sources and one of each of said pairs of resistance elements, first conductor means connecting in series the one 01' said first pair of re-,- sistances connected in one of said pair of circuits and the one of said second pair of resistances con- 01' said pair of circuits, said resistances being connected by said conductor means so that the potential drops across them are in opposition and the potential across the two re sistances in series is a measure of the difference between said inlet and outlet temperatures, additional conductor means connecting in series the group of two resistances connected by said first conductor means and the impedance between said second contact and said one end of said first element so that the potential across said group of two resistances opposes the potential between said contact and said one end of said first element, to the difference of said last-mentioned opposed potentials for controlling the rate of flow of combustion air to said engine.

10. Control apparatus for an internal combustion engine having an air compressor for supplying combustion air thereto. comprising manually operable means for controlling the quantity of fuel supplied to said engine per revolution, means for measuring the torque required to drive said compressor, means including a first electrical network associated with said manually operable means and said torque measuring means for producing a first electrical potential varying as the ratio of said torque to said quantity of fuel supplied per revolution, means for measuring the temperature increase of the air passing through said compressor, means including a second electrical networkassociated with said temperature measuring means for producing a second electrical potential varying as said temperature increases, and electrical means for balancing said potentials against each other and for controlling the now 'ol combustion airthrough said compressor in accordance with the balance or unbalance of said potentials. I a

11. Control apparatus for an engine having an air compressor for supplying combustion air thereto, comprising means for measuring the rise in temperature or the air in passing through said compressor (Ta-T1) means tor measuring the torque (L) required to drive said compressor, means for measuring the fuel flow to said engine per revolution thereof (0) means for controlling I theflow of air to said engine, means for controlwhere K is a constant.

ling the flovfot iuel to said engine, a manual operator for one oi! said controlling means, motor means for positioning the other-0t said controlling 'means,'and means including all said measur-.

ing means for controlling said'motor means to maintain the relationship:

LEIGHTON LEE, 1:. 

